When a group of people x number of drinks like Kool-Aid. Get laxatives and pour them into one of the drinks. Make sure no one knows what glass has them in. Wait until someone shits and has explosive Diarrhea.

Adam: lets play laxative rouletteGroup of kids: yea ok
(everyone drinks) (an hour or so goes by)
Kyle: Fuck i have to take a shit
(times goes by)
Kyle: that shit was explosive